Lead-acid batteries have been in use for a wide variety of applications. For example, such cells and batteries have been used in what are termed "stationary" battery applications wherein the lead-acid cells and batteries provide stand-by power in the event of a power failure. For this type of application, such stationary batteries are maintained at a full state-of-charge and in a ready-to-use condition, typically by float maintenance charging at a constant preset voltage. By way of illustration, such stationary batteries may be used in telecommunications, utilities, and the like. Lead-acid batteries have also been increasingly used in "on-the-road" and "off-the-road" electrical vehicles for forklift trucks, automated guided vehicles, and pure electric vehicles, whereby these batteries supply all the energy requirements. Such applications (often termed "motive power" applications) require repetitive deep discharge cycling.
Further, in some of these applications, the voltage requirements vary from two, four, six, and twelve volts. Commonly, previous designs had used different containers, assembly equipment and elements to achieve the varying voltages.
Utilizing such prior approaches requires the battery manufacturer to have substantial in-plant equipment, tooling, and container molds. Additionally, there are inventory issues to cope with, including maintaining an appropriate inventory of containers. Still further, managing the manufacturing line changeovers to provide the batteries with the desired varying voltages can decrease the productivity.
Issues also arise regarding the ability of conventional lead-acid battery assembly equipment to handle the sheer physical size and/or weight as the plate count is increased to provide the desired voltage. As one illustrative example, an element for a typical 12-volt, BCI Group 27 battery would have 17 plates. The plate count increases as voltage is reduced, viz., a 6-volt battery would have 34 plates/element, a 4-volt battery 51 plates/element, and a 2-volt battery 102 plates/element. This increasing element size and weight cannot be handled by conventional assembly equipment.
Automating the assembly process has been accordingly difficult for applications requiring such varying voltages. This lack of automation presents particular productivity difficulties where the volume of production is relatively small.
There accordingly exists the need for a facile method and battery in which the voltage can be varied from two, four, six, and twelve volts. It would be particularly desirable to develop such methodology in which existing equipment for assembling lead-acid batteries can be used.
Accordingly, it is an object of the present invention to provide a lead-acid battery standardized on a 12-volt element size and container, yet capable of being assembled so as to provide a voltage of two, four, or six, as well.
Another object of this invention is to provide a method for making lead-acid batteries of varying voltage which can be processed using conventional battery assembly equipment.
A still further object lies in the provision of a method for making lead-acid batteries with different selected voltages which substantially reduces manufacturing changeovers and downtime when an application requires the selection of a different voltage.
Other objects and advantages of the present invention can be seen from the following description of the invention.